Blood Pressure Changes After Automatic and Fixed CPAP in Obstructive Sleep Apnea: Relationship with Nocturnal Sympathetic Activity

Abstract

Treatment of obstructive sleep apnea (OSA) by continuous positive airway pressure (CPAP) usually causes a reduction in blood pressure (BP), but several factors may interfere with its effects. In addition, although a high sympathetic activity is considered a major contributor to increased BP in OSA, a relationship between changes in BP and in sympathetic nervous system activity after OSA treatment is uncertain. This study was undertaken to assess if, in OSA subjects under no pharmacologic treatment, treatment by CPAP applied at variable levels by an automatic device (APAP) may be followed by a BP reduction, and if that treatment is associated with parallel changes in BP and catecholamine excretion during the sleep hours. Nine subjects underwent 24-h ambulatory BP monitoring and nocturnal urinary catecholamine determinations before OSA treatment and 2 months following OSA treatment by APAP (Somnosmart2, Weinmann, Hamburg, Germany). Eight control subjects were treated by CPAP at a fixed level. After APAP treatment, systolic blood pressure (SBP) decreased during sleep (p < 0.05), while diastolic blood pressure (DBP) decreased both during wakefulness (p < 0.05) and sleep (p < 0.02). Similar changes were observed in subjects receiving fixed CPAP. Nocturnal DBP changes were correlated with norepinephrine (in the whole sample: r = .61, p < 0.02) and normetanephrine (r = .71, p < 0.01) changes. In OSA subjects under no pharmacologic treatment, APAP reduces BP during wakefulness and sleep, similarly to CPAP. A reduction in nocturnal sympathetic activity could contribute to the reduction in DBP during sleep following OSA treatment.

• ambulatory blood pressure monitoring
• catecholamines
• auto-CPAP
• obstructive sleep apnea
• treatment

ACKNOWLEDGMENTS

The authors are grateful to Giovanni Sciortino for his technical work. This study was supported by the Italian National Research Council, IBIM, order number ME.P01.014.002.

Declaration of interest: Weinmann Geräte für Medizin GmbH + Co. KG (Hamburg, Germany) sustained expenses for materials used in sleep studies, reagents, and ventilators for this research, and for participation of Dr. Marrone and Professor Bonsignore to scientific meetings, but in no way participated in the collection, analysis, and interpretation of data.